The suitability for large-scale screening and the transparent nature during embryonic and larval stages make zebrafish an attractive system for small molecule screening in an intact organism, with aims both to identify therapeutic compounds and to understand biological mechanisms. DA neurons degenerate in human Parkinson's disease (PD), a devastating neurodegenerative disorder for which there is currently no cure. Zebrafish, as a prominent vertebrate model organism with the ability to produce a large number of transparent embryos and larvae, is ideally suited for discovering small molecules that can regulate the development, maintenance, or regeneration of DA neurons. However, key limitations with whole organism-based chemical screening is low throughput and low resolution. In this proposal, we will advance whole organism screening by developing and integrating fast speed high-resolution whole-organism imaging with an improved microfluidics- based technology, using the DA neuron assay that we have already established. If successful, this platform will revolutionize the whole-organism screening capability and lead to novel small molecule compounds that can modify CNS development and function and provide leads for potential treatment of PD.